Use resource pack logic to load the layouts.
Finally delete the old screen defs, replace with builtin layout JSON files.
Include a top-aligned layout as a builtin resource pack.
Implement more possibilites for the layout to support said pack.

Instead of creating a new widget instance every frame, instantiate once and update content.
This means that every widget had to be updated to work like that.
This also necessitated some ugly hackery for the dwarven HUD.
Many other minor things like moving and renaming classes

The game launches successfully without any crashes!